Introduction
Filtering is a type of signal processing that is achieved by directing the signal through electronic circuitry to :
Modify its frequency spectrum and, consequently, its shape.
Adjust its phase, thereby altering its form.
Extract specific information associated with the signal.
Eliminate or reduce undesired spurious frequencies.
Isolate the useful frequency band(s) in a complex signal.
Filtering is applicable to signals represented in analogueue form (analogueue filters) or in digital form after sampling the signal (digital filters).
There are several categories into which analog filters can fall :
Passive filters: These primarily utilise high-quality inductors and capacitors. Until the 1970s, these were the exclusive designs, and they are still employed for high frequencies, particularly using quartz.
Active filters: Comprising capacitors, resistors, and active elements, primarily operational amplifiers (AILs), active filters are less bulky, easier to design, and more cost-effective than passive filters. However, due to AIL limitations, they typically operate at a frequency of less than 1 MHz, consume more power, and require a power source.
Applications :
Telecommunications systems (telephone, television, radio, data transmission, etc.)
Systems for acquiring and processing physical signals (medical monitoring, measuring systems, radars, etc.)
Power supply applications
Digital filters operate as linear combinations of samples. Filtering and spectral analysis are fundamental techniques in digital signal processing.